Homeowner Resources

Assessment of Property


Appraisers of the Assessor-County Clerk-Recorder's Office, Assessor's Division compile property tax assessments once a year, no later than July 1, for delivery to the County Auditor. This "Local Assessment Roll" covers more than 240,000 assessments county-wide valued in excess of $100 billion.


A copy of the Local Assessment Roll is available at the front counter of of the Assessor's Division for public inspection. The Assessor's Division also reassesses personal property each year.


The assessment process was substantially modified by the state-wide Proposition 13 of 1978. Proposition 13 limited annual increases of property assessments to no more than 2 percent.


But it also allowed property values to be reappraised if:


  • A change in ownership occurs; or
  • New construction is completed; or
  • New construction is unfinished on January 1st (Jan. 1 is known as the "lien date"); or
  • It is part of an annual review of properties having declining value; or
  • It is part of land conservation contract (Williamson Act).

Property Tax


The assessed value of property impacts the property tax liability. To look up the property tax amount, go to the following site: San Mateo County -- Tax Collector


Change in Ownership or New Construction


The Assessor must make an assessment whenever there is a reappraisal of real property due to a change in ownership or completion of new construction. This additional assessment is called a "Supplemental Assessment" and reflects the difference between the "base year value factored" and the new value. The supplemental assessment generates a supplemental tax bill pro-rated based on the number of months remaining in the fiscal year, ending June 30. This assessment is in addition to the regular tax bill or a tax refund. Usually there is only one supplemental assessment per change in ownership or new construction. However, events occuring in January, February, March, April and May affect two fiscal years and require two supplemental assessments.


When there is new construction, or an addition, to a structure, only the value of the new addition is added to the current assessed value. The value of the pre-existing property is unchanged.


Home Sales, Real Estate Loans and Mortgages


The Assessor often has a role in home sales and the mortgage process. Financial institutions need to insure that there is sufficient value in a property to cover a loan. Generally, this requires an appraisal and often involves a bank, or "fee," appraiser. The Assessor's Division does not have access to those appraisals and occasionally sends out a staff appraiser to look at the property. This review helps the Assessor establish a fair assessment for the property. Appraisers from the Assessor's Division carry identification.